The Research Plan will be composed of three studies which will complement each other. The goal of the research is to gain new insights into the dynamic mechanisms of normal and abnormal cerebral function by the application and correlation of the following measures: magnetoencephalography (MEG), cerebral sensory evoked potentials and positron emission computed tomography (PCT). The magnetoencephalogram (MEG) will be studied simultaneously with the EEG in both focal epilepsy and generalized epilepsy patients to see if the MEG is better localizing than the EEG for focus of seizure onset and if the MEG current patterns suggest an underlying generator in generalized "petit mal" seizures. The MEG and EEG of the focal interictal spike will be compared with each other and correlated with pathology, depth electrode seizure onsets and PCT in those patients with medically refractory seizures being evaluated for epilepsy surgery at UCLA. The temporal component of the long-latency auditory evoked potential (T-Complex) will be studied before and after anterior temporal lobectomy in the same epilepsy surgery group as mentioned above to determine if the T-Complex is generated inside or outside the volume of resection. The T-Complex will be studied in the same patients as above who have focal temporal hypometabolism on PCT to determine if the interictal zones of hypometabolism represent areas of decreased inhibition or decresed excitation, since ipsilateral T-Complex response appears to be primarily IPSPs and contralateral T-Complex appears to be primarily EPSPs. There are important practical aspects of the above localization and investigation of mechanisms in clinical epilepsy treatment.